Quorum sensing-disrupting compounds protect larvae of the giant freshwater prawn Macrobrachium rosenbergii from Vibrio harveyi infection

Vibriosis outbreaks caused by Vibrio harveyi and related species are amongst the major obstacles for the further expansion of giant freshwater prawn (Macrobrachium rosenbergii) larviculture. Vibrio harveyi regulates virulence gene expression through quorum sensing, bacterial cell-to-cell communication, and consequently, quorum sensing disruption has been suggested as an alternative strategy to control infections caused by these bacteria. Previous studies have shown that quorum sensing-disrupting compounds are able to disrupt quorum sensing in Vibrio harveyi. In this study, we demonstrated that the quorum sensing-disrupting compounds cinnamaldehyde, (Z-)-4-bromo-5-(bromomethylene)-2(5H)-furanone and (Z)-4-((5-(bromomethylene)-2-oxo-2,5-dihydrothiophen-3-yl)metoxy)-4-oxobutanoic acid increased the survival of giant freshwater prawn larvae when challenged to pathogenic Vibrio harveyi. Our in vivo challenge test showed that cinnamaldehyde and the thiophenone can protect the larvae from Vibrio harveyi infection when dosed to the culture water at 1 μM and 10 μM, whereas the brominated furanone offered protection at 1 μM but resulted in complete mortality at 10 μM. Although there were significant differences in survival between challenged larvae with and without addition of quorum sensing-disrupting compounds, there were no differences in growth (as determined by the larval stage index).